This invention relates to a process for filling a muffler shell with fibrous material, a muffler shell filled with fibrous material and a vacuum-filling device adapted for use during a muffler shell filling operation.
U.S. Pat. No. 4,569,471 to Ingemansson et al. describes a process and apparatus for feeding lengths of a continuous glass fiber strand into a muffler outer shell. The apparatus includes a nozzle for expanding the fiber strand into a wool-like material before the material centers the outer shell. In a first embodiment, filling of an outer cylinder 14 of the muffler shell occurs without an end-piece joined to the outer cylinder 14. After the filling operation is completed, the outer cylinder 14 is moved to a separate station where the end piece is welded onto the outer cylinder 14. In a second embodiment, illustrated in FIG. 3, a perforated pipe/outer end piece assembly is located only part way in the muffler outer cylinder 14 during the glass material filling operation. After the filling operation has been completed, the perforated pipe/end piece assembly is moved to its final position within the outer cylinder 14.
The ""471 patent process is acceptable when filling a muffler shell of the type including a separate end piece or perforated pipe/outer end piece assembly. However, the process is typically not used with clam shell mufflers comprising first and second halves which, when coupled together and enclosing a perforated pipe, do not have an open end through which fibrous material may be fed.
It is also known in the prior art to form preforms from glass material which are adapted to be inserted into a first muffler shell section prior to it being coupled to a corresponding second shell section; see U.S. Pat. No. 5,766,541, the disclosure of which is incorporated herein by reference. While such preforms are acceptable in performance, they add additional cost to the muffler due to the manufacturing steps necessary to form the preforms.
It is also known to fill bags or a mesh with fibrous material. The filled bag or mesh is then inserted into a first muffler shell section prior to the first shell section being coupled to a second shell section, see U.S. Pat. No. 6,068,082, the disclosure of which is incorporated herein by reference.
Hence, there is a need for an improved, low-cost muffler outer shell filling process which can be used to fill muffler shells such as clam-type muffler shells.
This need is met by the present invention, wherein a process is provided for filling a clam-type muffler shell using a vacuum-filling device. The device comprises a perforated tool and a vacuum apparatus adapted to receive the tool and apply a partial vacuum to a first surface of the tool. A sheet covers most, but preferably not all, openings provided in the perforated tool. The vacuum functions to maintain the sheet positioned adjacent to the tool. An internal structure, comprising one or more perforated elements such as one or more perforated pipes, is placed on the sheet and tool. A first muffler shell outer part is positioned adjacent to the tool such that a temporary inner cavity is defined by the tool and the first outer part. The inner cavity is then filled with fibrous material. Subsequent to the filling operation, the partial vacuum applied to the tool is removed. After the vacuum is removed from the tool, a partial vacuum is applied to the internal structure. The vacuum causes the fibrous material and the sheet to be drawn inwardly towards the internal structure. The first outer part, internal structure, fibrous material and sheet are then removed from the tool. If any portion of the sheet or fibrous material extends outwardly beyond the outer edge of the first part, the sheet and/or fibrous material is repositioned or moved inwardly so that it no longer extends beyond the outer edge. A second muffler shell outer part is then placed on the first part. The partial vacuum applied to the internal structure may be removed at this juncture. The first and second muffler shell parts are then coupled together such as by welding, flange crimping or fasteners. It is noted that any fibrous material extending out beyond the outer edges of the first and second muffler shell outer parts may have a detrimental impact on the weld at that point, i.e., may cause a void in the weld, and exposed fibers are aesthetically undesirable.
In accordance with a first aspect of the present invention, a process is provided for filling a muffler shell with fibrous material. The process involves providing a muffler shell comprising first and second muffler shell outer parts which define an internal cavity when coupled together and an internal structure adapted to extend at least part way through the shell internal cavity and having one or more openings communicating with the shell internal cavity. The process further comprises the steps of: providing a perforated tool having opposing first and second surfaces; providing a vacuum apparatus which is adapted to receive the perforated tool and apply a partial vacuum to the first surface of the tool; placing a sheet adjacent the second surface of the perforated tool; applying a partial vacuum to the first surface of the tool via the vacuum apparatus so as to draw the sheet against the tool second surface; placing the internal structure adjacent the tool; placing the first muffler shell outer part adjacent the tool such that the tool and the first part define a temporary inner cavity; feeding fibrous material into the temporary inner cavity; deactivating the vacuum apparatus; drawing a partial vacuum through the internal structure so as to draw the fibrous material and the sheet toward the internal structure; separating the first muffler shell outer part, the internal structure, the fibrous material and the sheet from the tool; and coupling the second muffler shell part to the first muffler shell part.
The fibrous material feeding step may comprise the steps of: providing a texturizing device having a nozzle; feeding continuous strand material and pressurized air into the texturizing device such that a wool-type product emerges from the nozzle; and positioning the nozzle adjacent to or in the temporary internal cavity such that the wool-type product is fed into the temporary internal cavity.
The vacuum apparatus may comprise a structure having an inner cavity communicating with a first vacuum source. The structure may further include an edge portion defining an opening to the inner cavity. The edge portion is adapted to receive the tool.
Preferably, the vacuum apparatus is deactivated after the fibrous material feeding step.
The step of drawing a partial vacuum through the internal structure may comprise the step of connecting the first vacuum source to the internal structure. Alternatively, the step of drawing a partial vacuum through the internal structure may comprise the step of coupling a second vacuum source to the internal structure.
The perforated tool preferably has a plurality of openings formed in it. The step of placing a sheet adjacent the second surface of the perforated tool may comprise the step of placing the sheet over the second tool surface such that the sheet covers at least a portion of the openings in the tool. If the sheet has either no perforations or only very small and/or a limited number of perforations, it is preferred that the sheet cover only a first portion of the openings in the tool such that a second portion of the openings is left uncovered. The second portion of openings allow a partial vacuum to be drawn within the temporary inner cavity such that the fibrous material is drawn inwardly into the cavity and compacted therein.
The step of placing the internal structure adjacent to the tool comprises the step of placing the internal structure in the tool over the sheet.
The step of coupling the second muffler shell part to the first muffler shell part may comprise the steps of: placing the second muffler shell part adjacent the first muffler shell part such that the first and second muffler shell parts define an internal cavity containing the internal structure, the fibrous material and the sheet; and joining the first and second muffler shell parts to one another.
The process preferably comprises the additional step of discontinuing the step of drawing a partial vacuum through the internal structure after the step of placing the second muffler shell part adjacent the first muffler shell part.
The internal structure may comprise at least one perforated element such as one or more perforated pipes.
The internal structure may also comprise at least one partition defining at least two internal compartments within the muffler shell internal cavity. The at least one internal compartment may be left unfilled with fibrous material.
In accordance with a second aspect of the present invention, a muffler filled with fibrous material and a sheet in accordance with the process set out above is provided.
In accordance with a third aspect of the present invention, a muffler is provided comprising a muffler shell including first and second muffler shell outer parts which define an internal cavity. The second muffler shell outer part includes a first external surface and a second internal surface. An internal structure is adapted to extend at least part way through the shell internal cavity and has one or more openings communicating with the shell internal cavity. Fibrous material is filled in the internal cavity. A sheet extends only between the second internal surface of the second muffler shell part and the fibrous material, i.e., the sheet engages the second internal surface of the second muffler shell part but does not engage a substantial portion of an internal surface of the first muffler shell part. The sheet does not comprise a bag filled with and containing fibrous material. The sheet may or may not be perforated.
The fibrous material comprises a mineral fiber wool-type product.
The internal structure may comprise at least one partition defining at least two internal compartments within the muffler shell internal cavity. At least one of the internal compartments may be completely devoid of fibrous material.
In accordance with a fourth aspect of the present invention, a vacuum-filling device is provided which is adapted to be used during a muffler shell filling operation. The muffler shell comprises first and second muffler shell outer parts which define an internal cavity when coupled together. An internal structure is adapted to be positioned within the muffler shell internal cavity. The device comprises: a perforated tool having first and second surfaces; and a vacuum apparatus adapted to receive the perforated tool and apply a partial vacuum to the first surface of the tool.
The vacuum apparatus comprises a structure with an inner cavity that communicates with a first vacuum source. The structure further includes an edge portion defining an opening to the inner cavity. The edge portion is adapted to receive the tool.
The tool has generally the same shape as the second muffler shell outer part. Further, the tool has at least one opening for receiving a nozzle of a texturizing device.